Method and device for separating ion mass, and ion doping device

ABSTRACT

A hollow exciting current pathway in the form of a conductor is arranged outside of an ion deflection casing with a curved contour and having an inlet and an outlet. The conductor is composed of a widthwise spiral formation of conductors running through the inlet and outlet and along the curved contour with a result that a magnetic field which is uniform widthwise is formed in the ion deflection casing. An ion beam is introduced through between the conductors at the inlet into the hollow exciting current pathway. By the action of the magnetic field through the hollow exciting current pathway, the ion beam is bent depending upon mass of ions. The ion beam with desired mass is taken out through between the conductors at the outlet with a result that an ion beam greater in size can be ion mass separated uniformly.

TECHNICAL FIELD

The present invention relates to an ion mass separation process, an ionmass separator and an ion doping apparatus, enabling stable massseparation in an ion beam larger in size and particularly broader inwidth.

BACKGROUND ART

Ion doping or implanting apparatuses have been used for addingelectroactive elements to a semiconductor or adding atoms of an additiveto a substrate for adhesive joining of hardly adhesive material to thesubstrate.

Up to the present, however, there have been no ion mass separating, iondoping apparatus using an ion beam larger in size (for example, 300mm×800 mm). Conventionally employed in ion doping apparatuses is anon-mass-separation system using an ion beam for ion doping without ionmass separation or a magnetic filter system using a magnetic filter forsimple reduction in ratio of lighter ion species (for example, hydrogenions) in a plasma generating portion of an ion generator.

For example, in an ion doping apparatus for a semiconductor,hydrogen-diluted phosphine (PH₃) or diborane (B₂H₆) is used asplasma-generating source gas for an ion generator, which generates notonly desired PH_(x) and B₂H_(x) but also ion species such as H_(x),P₂H_(x) and BH_(x) in the plasma generating portion, a mixed beam ofsuch ion species being extracted from the plasma generating portion.Such existence of the ion species other than the desired ones will leadto a problem of nonuniformity in implantation depth distribution of Pand B through ion doping as well as a problem of imparting extra thermalload to a substrate.

Accordingly, it has been desired to promptly establish technique forstable mass separation in an ion beam larger in size and particularlybroader in width.

Meanwhile, there have been envisaged ion mass separators for ion beamssmaller in size. FIGS. 1 and 2 show an example of an ion mass separatorfor an ion beam smaller in size. In this ion mass separator 1, ionsgenerated in a plasma generating portion (not shown) are extracted andaccelerated by ion extraction electrodes 3 into an ion beam 4 which isguided to a small-sized, vacuum ion deflection pathway 5 via an inlet 6at one end thereof. Arranged outside of an intermediate portion of theion deflection pathway 5 is an electro-magnet 8 comprising an iron core7 a with a solenoid 7 b wound thereon. As shown in FIG. 2, magnetismgenerating portions 9 of the electro-magnet 8 are adjacent to the iondeflection pathway 5. Ions (charged particles) in the ion beam 4 movethrough the ion deflection pathway 5 to receive bending action indirections perpendicular to directions of magnetic field lines G in amagnetic field of the electromagnet 8 with a result that the ion beam 4is bent in the ion deflection pathway 5. In this respect, generating astrong magnetic field can cause the ion beam 4 to be bent with a greaterdeflection angle (90° in FIG. 1) with a result that ions with mass lessthan that desired are bent earlier and collide with a smaller-radiusside inner peripheral portion of the ion deflection pathway 5 forseparation whereas ions with mass greater than that desired fail to befully bent and collide with a larger-radius side inner peripheralportion of the ion deflection pathway 5 for separation. This enablesonly targeted ions to be accelerated by ion acceleration electrodes 10at the other end of the ion deflection pathway 5 and to be taken outthrough an outlet 11.

The take-out ion beam 4 from the ion mass separator 1 is used in an iondoping apparatus where operations such as convergence of the ion beam 4may be effected as needs demand and then irradiation to a substrate 12to be dealt with is effected to implant the ions into the substrate 12.In the ion doping apparatus 13, ion doping is effected over an extensivesurface of the substrate 12 through movement of the substrate 12 orelectrical scanning of the ion beam 4.

However, in the above-mentioned ion mass separator 1 using theelectromagnet 8 having the iron core 7 a with the solenoid 7 b woundthereon, magnetism generating portions 9 of the electromagnet 8 must beadjacent to the ion deflection pathway 5 for generation of the uniformmagnetic field lines G so as to form a stable and strong magnetic fieldfor bending of the ion beam 4; therefore, magnitude X of the ion beam 4in FIG. 2 in the direction of curvature radius may be increased to someextent by increasing in size the electromagnet 8 while widthwisemagnitude Y shown vertically in FIG. 2 cannot be increased. Morespecifically, increasing the widthwise magnitude Y would require spacingbetween the magnetism generating portions 9 to be increased as shown inFIG. 3; such increased spacing between the magnetism generating portions9 would lead to failure of forming an uniform magnetic field in the iondeflection pathway 5 due to deformation of the magnetic field lines Goutside, resulting in nonuniform bent of the ions and failure ofobtaining a stable ion beam 4. Thus, there have been no ion beam 4larger in size and uniformly ion mass separated since increase of thewidthwise magnitude Y is unavailable.

The present invention is made to solve such problems in the conventionalapparatuses and has its object to provide an ion mass separationprocess, an ion mass separator and an ion doping apparatus, enablinguniform ion mass separation in an ion beam larger in size.

SUMMARY OF THE INVENTION

Arranged outside of an ion deflection casing with a curved contour andhaving an inlet and an outlet is a hollow exciting current pathway inthe form of conductor means which is composed of a widthwise spiralformation running through the inlet and outlet and along the curvedcontour; an ion beam introduced between the conductors at the inlet isbent in the ion deflection casing for ion mass separation so that amagnetic field which is uniform widthwise can be formed even if the iondeflection casing is of a shape broader in width. As a result, the ionbeam broader in width can be bent uniformly widthwise, resulting inobtaining the high-quality ion beam which is broader in width anduniformly ion mass separated.

Moreover, ion doping can be effected by such high-quality ion beamuniformly ion mass separated and having no extra ion species so thatimplantation depth distribution of ions can be made uniform and extrathermal load is prevented from being imparted to a substrate. The ionbeam broader in width enables ion doping to be effected over anextensive area of a substrate in a single operation, therebysubstantially improving operation efficiency.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic side view of a conventional ion mass separator andion doping apparatus;

FIG. 2 is a view looking in the direction of arrows II in FIG. 1;

FIG. 3 is an explanatory view showing a state of spacing being increasedbetween magnetism generating portions of an electromagnet shown in FIG.2;

FIG. 4 is a sectional side view showing an embodiment of an ion massseparator and ion doping apparatus according to the invention;

FIG. 5 is a perspective view showing a spiral formation of conductormeans;

FIG. 6 is a partial detailed view of an inlet shown in FIG. 4;

FIG. 7 is a view looking in the direction of arrows VII in FIG. 6; and

FIG. 8 is a schematic diagram showing an embodiment of a trapezoidalcurrent pathway.

BEST MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments of the invention will be described in conjunctionwith drawings.

FIG. 4 is a schematic view showing an ion mass separator 14 and an iondoping apparatus 15 using the same according to the invention in whichreference numeral 16 denotes an ion generator with a plasma generatingportion; and 17, an ion deflection casing.

The ion deflection casing 17 shown in FIG. 4 has a substantiallyfan-shaped side contour to provide a broader space which is long in adirection perpendicular to plane of the drawing. The substantiallyfan-shaped contour has linear end portions which provide an inlet 18 andan outlet 19, the inlet 18 being connected to the ion generator 16. Theinlet 18 and the outlet 19 are angularly displaced with each other by,for example, 90° for deflection of the ion beam 4 with the greaterangle.

Conductor means 20 is arranged outside of the ion deflection casing 17and is composed of a spiral formation of components mutually spacedapart widthwise at predetermined intervals, the spiral formation runningthrough the inlet 18 and the outlet 19 and along the curved contour asshown in FIGS. 4 and 5, thereby providing a hollow exciting currentpathway 21 which is broader in the direction perpendicular to the planeof the drawing. Thus, the hollow exciting current pathway 21 shown inFIG. 4 provides a fan-shaped current pathway 21A.

In the fan-shaped current pathway 21A shown in FIG. 4, the spiralformation is provided by sequentially interconnecting, via connectors22, outer arcuate conductors 20 a arranged at required intervals andoutside of a larger-radius side portion of the ion deflection casing 17,inner arcuate conductors 20 b arranged at required intervals and outsideof a smaller-radius side portion of the ion deflection casing 17, andlinear conductors 20 c and 20 d arranged at required intervals forformation of linear portions 20′ in the inlet 18 and the outlet 19.

As detailedly shown in FIGS. 6 and 7, each conductor of the conductormeans 20 is in the form of rod and comprises a conductive core 23 and anouter conductor portion 24 for surrounding the conductive core 23,deionized water being supplied between the conductive core 23 and theouter conductor portion 24. Isolation material 25 at the connectors 22provides isolation between the conductive core 23 and outer conductorportion 24 while the respective outer conductor portions 24 areelectrically interconnected to thereby shield electric potential of thehollow exciting current pathway 21.

As shown in FIG. 7, required spacing S is provided between each of thelinear conductors 20 c and 20 d at the inlet 18 and outlet 19; ions fromthe ion generator 16 are introduced into and out of the ion deflectioncasing 17 through such spacings S.

As shown in FIG. 4, arranged between the linear conductors 20 c in theinlet 18 and the ion generator 16 are rod-like ion extraction electrodes26 so as to be positioned in a relationship spaced apart from each otherand overlapped with the linear conductors 20 c.

Arranged adjacent to the outlet 19 are ion acceleration electrodes 27.Each of the linear conductors 20 d in the outlet 19 shown in FIG. 4 isprovided at its opposite sides (left and right in the figure) withshielding members 28 which partly block off interspaces between thelinear conductors 20 d to leave an ion extraction port 29.

The ion deflection casing 17, which constitutes the fan-shaped currentpathway 21A, has widthwise opposite inner ends along each of whichextends a neutralizing electronic supply 30 in the form of, for example,filament for neutralizing space charge of the ion beam 4.

The above-mentioned ion mass separator 14 may be employed in an iondoping apparatus 15 where operations such as convergence of the ion beam4, which is mass separated in the ion mass separator 14, may be effectedas needs demand and then irradiation to a substrate 12 to be dealt withis effected to implant the ions into the substrate 12.

Next, the mode of operation of the above embodiment will be described.

In the ion mass separator 14 shown in FIG. 4, ions generated in theplasma generating portion in the ion generator 16 are extracted andaccelerated by the ion extraction electrodes 26 at the inlet 18,introduced, while accelerated by the linear conductors 20 c, through thespacings S between the linear conductors 20 c into the ion deflectioncasing 17 of the fan-shaped current pathway 21A and undergo bending bythe action of the hollow exciting current pathway 21. The ion beam 4thus bent is extracted and accelerated by the ion accelerationelectrodes 27 at the outlet 19 to be taken out outside. It is alsoaccelerated by the linear conductions 20 d at the outlet 19.

As shown in FIG. 4, the hollow exciting current pathway 21 is arrangedoutside of the ion deflection casing 17 and is constituted by awidthwise spiral formation (FIG. 5) of conductor means 20 runningthrough the inlet 18 and outlet 19 and along the curved contour, whichleads to forming a magnetic field within the ion deflection casing 17which has magnetic field lines extending widthwise and perpendicular tothe plane of the drawing of FIG. 4. As a result, this magnetic field hasstrength which is uniform widthwise of the fan-shaped current pathway21A. In this connection, the outer conductor portions 24 surrounding theconductive cores 23 in the conductor means 20 are electricallyinterconnected to shield electric potential of the fan-shaped currentpathway 21A so that any voltage potential difference in the fan-shapedcurrent pathway 21A exerts no influence on beam trajectory.

Thus formed magnetic field in the fan-shaped current pathway 21A, whichis uniform widthwise, causes ions in the ion beam 4 to receive bendingforce in accordance with mass thereof and uniform widthwise of thefan-shaped current pathway 21A and to be bent uniform. As shown in dotlines in FIG. 4, ions with mass less than that desired are bent earlier,collide with a smaller-radius side inner peripheral portion of the iondeflection casing 17 and are neutralized by the neutralizing electronicsupplies 30; ions with mass greater than that desired fail to be fullybent, collide with a larger-radius side inner peripheral portion of theion deflection casing 17 and are neutralized by the neutralizingelectronic supplies 30.

As a result, only ions with desired mass shown by solid lines are led tothe outlet 19 at the other end of the ion deflection casing 17. Sincethe ion extraction port 29 is provided by the linear conductors 20 d atthe outlet 19 partly having the shielding members 28, desired ions canbe further accurately separated for take-out by selecting a size and aposition of the ion extraction port 29 and selecting strength of themagnetic field of the conductor means 20.

Thus, according to the above-mentioned ion mass separator 14, thehigh-quality ion beam 4 which is larger in size and particularly broaderin width and is uniformly ion mass separated can be taken out.

In an ion doping apparatus 15 using the ion mass separator 14, an ionbeam 4 generated in the ion mass separator 14 may undergo operationssuch as convergence as need demands, and then is irradiated withscanning onto a substrate 12 to be dealt with so as to implant the ionsto the substrate 12. Because of the ion beam 4 being composed only bydesired ions including no extra ion species, implantation depthdistribution of ions can be made uniform upon ion doping and extrathermal load is prevented from being imparted to the substrate 12. Theion beam 4 broader in width enables ion doping to be effected over anextensive area of a substrate 12 in a single operation, therebysubstantially improving operation efficiency.

The sectional shape of the hollow exciting current pathway 21 is notlimited to be substantially fan-shaped as shown in FIG. 4 and may bevarious; preferably, it is at least of a shape which allows deflectionwith a greater angle (for example, 90°). The components of the conductormeans 20 arranged at the inlet 18 and outlet 19 preferably provideslinear portions 20′.

FIG. 8 shows an embodiment wherein the hollow exciting current pathway21 is a trapezoidal current pathway 21B which has longer- andshorter-side conductors 20 e and 20 f which in turn are interconnectedat their ends by linear conductors 20 c and 20 d at the inlet 18 andoutlet 19. Such a structure also has functions similar to those of thefan-shaped current pathway 21A shown in FIG. 4.

Industrial Applicability

An ion beam larger in size can be uniformly mass separated so that uponion doping implantation depth distribution of ions can be made uniformand extra thermal load is prevented from being imparted to a substrate.The ion beam broader in size enables ion doping to be effected over anextensive area of a substrate in a single operation, therebysubstantially improving operation efficiency.

1. An ion mass separation process comprising: arranging a hollowexciting current pathway in a form of a conductor outside of an iondeflection casing with a curved contour and having an inlet and anoutlet, said conductor is composed of a widthwise spiral formation ofconductors running through the inlet and outlet and along the curvedcontour, thereby forming a magnetic field in the ion deflection casingwhich is uniform widthwise, introducing an ion beam through between theconductors at the inlet into the ion deflection casing so as to be benttherein depending upon mass of ions by action of the magnetic fieldthrough the hollow exciting current pathway; and taking out the ion beamwith desired mass through between the conductors at the outlet.
 2. Anion mass separator comprising: a hollow exciting current pathway in aform of a conductor arranged outside of an ion deflection casing with acurved contour and with an inlet and an outlet, wherein said conductoris composed of a widthwise spiral formation of conductors runningthrough the inlet and outlet and along the curved contour, ionextraction electrodes arranged adjacent to the inlet, an ion generatoradjacent to the ion extraction electrodes, and ion accelerationelectrodes arranged adjacent to the outlet.
 3. An ion doping apparatuscomprising an ion mass separator according to claim 2 by which an ionbeam is mass separated to be irradiated to a substrate for ionimplantation.
 4. An ion mass separator according to claim 2, whereineach of the conductors comprises a conductive core and an outerconductor portion surrounding said conductive core, the respective outerconductor portions being electrically interconnected to shield electricpotential of the hollow exciting current pathway.
 5. An ion dopingapparatus comprising an ion mass separator according to claim 4 by whichan ion beam is mass separated to be irradiated to a substrate for ionimplantation.
 6. An ion mass separator according to claim 2, wherein theconductors at the inlet and outlet provide linear portions.
 7. An iondoping apparatus comprising an ion mass separator according to claim 6by which an ion beam is mass separated to be irradiated to a substratefor ion implantation.
 8. An ion mass separator according to claim 2,wherein the hollow exciting current pathway is a fan-shaped currentpathway that includes outer and inner arcuate conductors and linearconductors arranged at the inlet and outlet for connecting ends of thearcuate conductors.
 9. An ion doping apparatus comprising an ion massseparator according to claim 8 by which an ion beam is mass separated tobe irradiated to a substrate for ion implantation.
 10. An ion massseparator according to claim 2, wherein the hollow exciting currentpathway is a trapezoidal current pathway that includes longer-side andshorter-side conductors and linear conductors arranged at the inlet andoutlet for connecting ends of the longer-side and shorter-sideconductors.
 11. An ion doping apparatus comprising an ion mass separatoraccording to claim 10 by which an ion beam is mass separated to beirradiated to a substrate for ion implantation.
 12. An ion massseparator according to claim 2, wherein the conductors at the outlet arepartially shielded by shielding members to leave an ion take-out port.